<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">
//window = null;
//alert(window)
//top = null;
//parent = null
//self = null;
//this = null;
                 //bei yin  ->wangyuechaode window
                 //top - window
//wangyuechao -> zhangruixi
console.log(this);

//alert(window == self)



</script>
</body>
</html>